CN102868167B - Reactive voltage control method of photovoltaic power station - Google Patents

Abstract

The invention discloses a reactive voltage control method of a photovoltaic power station, which uses a photovoltatic power station synchronization point as a control target and reactive power as a regulating quantity. According to the reactive demand of the photovoltaic power station, a reactive power supply of the photovoltaic power station is integrally planed, the reactive output of each photovoltaic inverter and reactive compensating device in the photovoltaic power station is determined, and coordination control of the photovoltaic inverters and the reactive compensating devices in the photovoltaic power station is realized; and protection restraint conditions of the photovoltaic inverters and the reactive compensating devices are fully considered, and the photovoltaic inverters and the reactive compensating devices, which do not meet the restraint conditions, do not participate in the reactive voltage control. The control method provided by the invention can ensure that the reactive output of the photovoltaic power station synchronization point meets the system load change and inhibits the bus voltage fluctuation caused by load change, and has the function of maintaining the voltage of the photovoltaic power station synchronization point to be stable.

Description

Photovoltaic plant reactive power/voltage control method

Technical field

The present invention relates to a kind of photovoltaic plant reactive power/voltage control method, belong to photovoltaic power generation technology field.

Background technology

In recent years, photovoltaic generation generated electricity and was greatly developed as renewable and clean energy resource.Photovoltaic generation has randomness, intermittence and uncontrollability, and the extensive access of photovoltaic generation brings very large impact to the safe operation of electric power system, and wherein reactive voltage problem is exactly of greatest concern, is also one of problem the most common in actual motion.

Along with the development of photovoltaic power generation technology, photovoltaic DC-to-AC converter has been realized meritorious, idle decoupling zero control, can independently regulate meritorious, idlely, and photovoltaic DC-to-AC converter can be used as the important reactive power source of photovoltaic plant.But in actual motion, photovoltaic DC-to-AC converter substantially and have neither part nor lot in idle adjusting, causes large capacity low cost reactive capability idle.

Early stage photovoltaic plant carries out reactive power/voltage control by switched capacitor, low-response, regulates unsmoothly, cannot realize the optimal compensation state system is in service.At present, newly-built photovoltaic plant has all been equipped with dynamic reactive compensation device, as SVC, SVG etc., to improve the dynamic responding speed of idle adjusting.But, in point photovoltaic plant that many phases build, usually there is multiple SVC, SVG the situation of depositing, because multiple reactive power compensators are done things in his own way, lack and coordinate, when adjusting, very easily there is voltage concussion.

Summary of the invention

For the deficiencies in the prior art, the object of the invention is to, a kind of photovoltaic plant reactive power/voltage control method is provided, according to the reactive requirement of the photovoltaic electric station grid connection point calculating, reactive power to photovoltaic plant is done unified planning, coordinate to control the idle output of interior every the photovoltaic DC-to-AC converter of photovoltaic plant and reactive power compensator, make the idle output of photovoltaic electric station grid connection point meet the variation of system loading, maintain photovoltaic electric station grid connection point voltage stable.

For solving the problems of the technologies described above, the technical solution used in the present invention is: photovoltaic plant reactive power/voltage control method, it is characterized in that, and the method comprises the following steps:

1) measure the voltage instantaneous value U of photovoltaic electric station grid connection point _mea, calculating voltage instantaneous value U _meawith grid-connected point voltage desired value U _targetthe absolute value of difference, be designated as voltage deviation Δ U=|U _mea-U _targrt|;

2) the dead band threshold values δ of voltage deviation is set, enters step 3) if voltage deviation Δ U is greater than dead band threshold values δ, otherwise return to step 1);

3) by the system impedance X between self study method identification photovoltaic plant and electrical network;

4) calculate photovoltaic plant Target of Reactive Power value Q _target, $Q_{t\arg \mathrm{et}}=\frac{U_{t\arg \mathrm{et}}\×(U_{t\arg \mathrm{et}}-U_{\mathrm{mea}})}{X}+\frac{Q_{\mathrm{mea}}}{U_{\mathrm{mea}}}\×U_{t\arg \mathrm{et}},$ Wherein, Q _meafor the idle instantaneous value of photovoltaic electric station grid connection point;

5) judge whether each photovoltaic DC-to-AC converter and reactive power compensator meet predefined protection constraints, the photovoltaic DC-to-AC converter and the reactive power compensator that do not meet described protection constraints do not participate in reactive power/voltage control;

6) idle according to the preferential photovoltaic DC-to-AC converter that regulates, secondly regulate the idle principle of reactive power compensator, by Target of Reactive Power value Q _targetcarry out just sub-distribution, between photovoltaic DC-to-AC converter and reactive power compensator, distribute;

7) according to the idle distribution principle of predefined unit, the result of first sub-distribution is carried out to sub-distribution again, respectively between photovoltaic DC-to-AC converter, distribute between reactive power compensator;

8) result of distributing according to photovoltaic DC-to-AC converter, reactive power compensator, sends idle control command to photovoltaic DC-to-AC converter and reactive power compensator;

9) after waiting for that photovoltaic DC-to-AC converter, reactive power compensator execution instruction have been moved, return to step 1).

Further technical scheme is:

In above-mentioned steps (3), described system impedance is arranged to upper lower limit value, in the time can not picking out system impedance, get its upper limit.

In above-mentioned steps (3), twice of the front and back voltage difference of system impedance is greater than 0.5% specified busbar voltage described in identification.

In above-mentioned steps (5), described protection constraints comprises the out-of-limit protective condition of analog quantity, quantity of state latch-up protection condition, communication disruption protective condition.

In above-mentioned steps (6), the concrete steps of described just sub-distribution are:

A) calculate every the photovoltaic DC-to-AC converter that participates in reactive power/voltage control in photovoltaic plant, the idle adjustable upper limit value and lower limit value of reactive power compensator;

B) calculate photovoltaic plant Target of Reactive Power value Q _targetwith idle instantaneous value Q _meadifference, be designated as idle increment Delta Q=Q _target-Q _meaif idle increment Delta Q is greater than zero, go to step c), if idle increment Delta Q is less than zero, go to step d);

C), according to the idle adjustable higher limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle increasing nargin summation Q that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, reactive power compensator idle increasing nargin summation Q _cmargin, computing formula is as follows:

$Q_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gi}\max }-Q_{\mathrm{Gimea}})$

$Q_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(Q_{\mathrm{Ci}\max }-Q_{\mathrm{Cimea}})$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value;

D), according to the idle adjustable lower limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle nargin summation Q that subtracts that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, the idle nargin summation Q that subtracts of reactive power compensator _cmargin, computing formula is as follows:

$Q_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gimea}}-Q_{\mathrm{Gi}\min })$

$Q_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Cimea}}-Q_{\mathrm{Ci}\min })$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value.

In above-mentioned steps (7), idle distribution principle comprises similar power factor, similar adjustment nargin, proportional with capacity.

Beneficial effect of the present invention is as follows:

1. the present invention is taking photovoltaic electric station grid connection point voltage as controlling target, using idle as adjustment amount.According to the reactive requirement of photovoltaic plant, to the reactive power source unified planning of photovoltaic plant, determine the idle output of interior every the photovoltaic DC-to-AC converter of photovoltaic plant and reactive power compensator, realize the coordination control of the interior photovoltaic DC-to-AC converter of photovoltaic plant and reactive power compensator;

2. control procedure of the present invention has fully taken into account the protection constraints of photovoltaic DC-to-AC converter and reactive power compensator, and the photovoltaic DC-to-AC converter and the reactive power compensator that do not meet constraints are not participated in to reactive power/voltage control;

3. control method of the present invention can make the idle output of photovoltaic electric station grid connection point meet system loading variation, and the busbar voltage that suppresses to be caused by load variations fluctuates, and has the stable effect of photovoltaic electric station grid connection point voltage that maintains.

Brief description of the drawings

Fig. 1 is the flow chart of photovoltaic plant reactive power/voltage control method of the present invention;

Fig. 2 is the structural representation of photovoltaic plant connecting system of the present invention.

Embodiment

For further disclosing technical scheme of the present invention, describe embodiments of the present invention in detail below in conjunction with accompanying drawing: the present invention is taking photovoltaic electric station grid connection point voltage as controlling target, using idle as adjustment amount.By the coordination control to photovoltaic DC-to-AC converter and reactive power compensator, make grid-connected point voltage meet line voltage requirement.

Be illustrated in figure 1 the flow chart of photovoltaic plant reactive power/voltage control method of the present invention.This method comprises the following steps:

1) measure the voltage instantaneous value U of photovoltaic electric station grid connection point _mea, calculating voltage instantaneous value U _meawith grid-connected point voltage desired value U _targetthe absolute value of difference, be designated as voltage deviation Δ U=|U _mea-U _target|.

2) the dead band threshold values δ of voltage deviation is set, enters step 3) if voltage deviation Δ U is greater than dead band threshold values δ, otherwise return to step 1).

3) by the system impedance X between self study method identification photovoltaic plant and electrical network.

Fig. 2 is the structural representation of photovoltaic plant connecting system, and X just represents that power station arrives the system impedance of bus.

If before adjusting for the s time, high voltage bus voltage U ^s-, send idle Q to system ^s-, after adjustment, be respectively U ^s+, Q ^s+, at this moment can write out equation and be: (Q ^s+/ U ^s+-Q ^s-/ U ^s-) X=(U ^s+-U ^s-).

Be provided with t time and adjust record, have

$\left[\begin{array}{c}.\\ .\\ (Q^{s+}/U^{s+}-Q^{s-}/U^{s-})\\ .\\ .\end{array}\right]X=\left[\begin{array}{c}.\\ .\\ (U^{s+}-U^{s-})\\ .\\ .\end{array}\right]$

Be abbreviated as [Δ Q/U] X=[Δ U]

[Δ Q/U] is multiplied by both sides ^t, after arrangement, can obtain

In system impedance self study identification, give one's full attention to and choose the validity of data and ageing, and determine that in conjunction with history run experience whether system impedance is reasonable.

Consideration in identification process, is mainly reflected in the following aspects:

1. it is arranged to upper lower limit value, in the time can not picking out system impedance, get its upper limit.

2. twice of the front and back voltage difference that ensures identification system impedance must be greater than the impedance of certain numerical value ability computing system, is rule of thumb set to 0.5% specified busbar voltage comparatively reasonable.

3. be a very difficult problem for the definite of t value, get how many times reasonable, neither one can standards of measurement.Rule of thumb can be set to 5.Because t value is rolling process forward, ensure the real-time of identification.

With respect to other algorithms, self-learning algorithm can find the parameter value of variation accurately, and then improves the precision of reactive power/voltage control.

4) calculate photovoltaic plant Target of Reactive Power value Q _target, computing formula is as follows:

$Q_{t\arg \mathrm{et}}=\frac{U_{t\arg \mathrm{et}}\×(U_{t\arg \mathrm{et}}-U_{\mathrm{mea}})}{X}+\frac{Q_{\mathrm{mea}}}{U_{\mathrm{mea}}}\×U_{t\arg \mathrm{et}}$

Wherein, Q _meafor the idle instantaneous value of photovoltaic electric station grid connection point.

5) judge whether each photovoltaic DC-to-AC converter and reactive power compensator meet predefined protection constraints, the photovoltaic DC-to-AC converter and the reactive power compensator that do not meet described protection constraints do not participate in reactive power/voltage control.

Above-mentioned protection constraints comprises the out-of-limit protective condition of analog quantity, quantity of state latch-up protection condition, communication disruption protective condition.For example, as high voltage bus voltage out-of-limit, answer lock-in control; Photovoltaic DC-to-AC converter or reactive power compensator protection action, answer lock-in control etc.

6) idle according to the preferential photovoltaic DC-to-AC converter that regulates, secondly regulate the idle principle of reactive power compensator, by photovoltaic plant Target of Reactive Power value Q _targetcarry out just sub-distribution, between photovoltaic DC-to-AC converter and reactive power compensator, distribute.Concrete steps are as follows:

A) calculate every the photovoltaic DC-to-AC converter that participates in reactive power/voltage control in photovoltaic plant, the idle adjustable upper limit value and lower limit value of reactive power compensator.

According to photovoltaic DC-to-AC converter real time execution operating mode and power factor adjustable extent, calculate the idle adjustable upper limit Q of every photovoltaic DC-to-AC converter _gimax, idle adjustable lower limit Q _gimin, computing formula is as follows:

$Q_{\mathrm{Gi}\max }=\frac{\sqrt{(1-{{\mathrm{\λ}}_{\mathrm{Gi}+}}^2)}}{{\mathrm{\λ}}_{\mathrm{Gi}+}}\×P_{\mathrm{Gimea}}$

$Q_{\mathrm{Gi}\min }=\frac{\sqrt{(1-{{\mathrm{\λ}}_{\mathrm{Gi}-}}^2)}}{{\mathrm{\λ}}_{\mathrm{Gi}-}}\×P_{\mathrm{Gimea}}$

Wherein, λ _gi+, λ _gi-be respectively photovoltaic DC-to-AC converter leading power factor limit value and lagging power-factor limit value, P _gimeafor the meritorious instantaneous value of photovoltaic DC-to-AC converter.

According to reactive power compensator constraints, calculate the idle adjustable upper limit Q of every reactive power compensator _cimax, idle adjustable lower limit Q _cimin, computing formula is as follows:

Q _Cimax=+Q _Ri

Q _Cimin=-Q _Ri

Wherein, Q _rifor reactive power compensator rated capacity.

B) calculate photovoltaic plant Target of Reactive Power value Q _targetwith idle instantaneous value Q _meadifference, be designated as idle increment Delta Q=Q _target-Q _meaif idle increment Delta Q is greater than zero, go to step c), if idle increment Delta Q is less than zero, go to step d).

C), according to the idle adjustable higher limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle increasing nargin summation Q that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, reactive power compensator idle increasing nargin summation Q _cmargin, computing formula is as follows:

$Q_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gi}\max }-Q_{\mathrm{Gimea}})$

$Q_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Ci}\max }-Q_{\mathrm{Cimea}})$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value.

First judge whether idle increment Delta Q is greater than Q _gmarginif be not more than Q _gmargin, the idle increment Delta Q of photovoltaic plant is born separately by photovoltaic DC-to-AC converter, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=Δ Q, the idle increment Delta Q that reactive power compensator is born _c=0;

If be greater than Q _gmargin, secondly judge whether idle increment Delta Q is greater than (Q _gmargin+ Q _cmargin), if be not more than (Q _gmargin+ Q _cmargin), the idle increment Delta Q of photovoltaic plant is by photovoltaic DC-to-AC converter and reactive power compensator shared, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=Q _gmargin, the idle increment Delta Q that reactive power compensator is born _c=Δ Q-Q _gmargin;

If be greater than (Q _gmargin+ Q _cmargin), the idle increment Delta Q of photovoltaic plant is by photovoltaic DC-to-AC converter and reactive power compensator shared, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=Q _gmargin, the idle increment Delta Q that reactive power compensator is born _c=Q _cmargin, go to step 7).

D), according to the idle adjustable lower limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle nargin summation Q that subtracts that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, the idle nargin summation Q that subtracts of reactive power compensator _cmargin, computing formula is as follows:

$Q_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gimea}}-Q_{\mathrm{Gi}\min })$

$Q_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Cimea}}-Q_{\mathrm{Ci}\min })$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value.

First judge the absolute value of idle increment Delta Q | whether Δ Q| is greater than Q _gmarginif be not more than Q _gmargin, the idle increment Delta Q of photovoltaic plant is born separately by photovoltaic DC-to-AC converter, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=Δ Q, the idle increment Delta Q that reactive power compensator is born _g=0;

If be greater than Q _gmargin, next judges the absolute value of idle increment Delta Q | whether Δ Q| is greater than (Q _gmargin+ Q _cmargin), if be not more than (Q _gmargin+ Q _cmargin), the idle increment Delta Q of photovoltaic plant is by photovoltaic DC-to-AC converter and reactive power compensator shared, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=-Q _gmargin, the idle increment Delta Q that reactive power compensator is born _c=Δ Q+Q _gmargin;

If be greater than (Q _gmargin+ Q _cmargin), the idle increment Delta Q of photovoltaic plant is by photovoltaic DC-to-AC converter and reactive power compensator shared, the idle increment Delta Q that photovoltaic DC-to-AC converter is born _g=-Q _gmargin, the idle increment Delta Q that reactive power compensator is born _c=Q _cmargin, go to step 7).

7) according to the idle distribution principle of predefined unit, the result of first sub-distribution is carried out to sub-distribution again, respectively between photovoltaic DC-to-AC converter, distribute between reactive power compensator.

Idle distribution principle mainly comprises similar power factor, similar adjustment nargin, proportional etc. with capacity.Below only taking similar adjustment nargin as example.

Similar adjustment nargin principle is to carry out without the distribution of work according to the idle allowance size of control object, remains idle manyly, provides many idle, remains idle less, provides few idle.Can ensure that so each control object has close Reactive Power Margin.

According to similar adjustment nargin algorithm, the idle output valve Q of photovoltaic DC-to-AC converter _gican be expressed as:

$Q_{\mathrm{Gi}}=\frac{Q_{\mathrm{Gi}\max }-Q_{\mathrm{Gimea}}}{Q_{\mathrm{Gm}\arg \mathrm{in}}}\×\mathrm{\Δ}{Q}_G+Q_{\mathrm{Gimea}}$

The idle output valve Q of reactive power compensator _cican be expressed as:

$Q_{\mathrm{Ci}}=\frac{Q_{\mathrm{Ci}\max }-Q_{\mathrm{Cimea}}}{Q_{\mathrm{Cm}\arg \mathrm{in}}}\×\mathrm{\Δ}{Q}_C+Q_{\mathrm{Cimea}}.$

8) result of distributing according to photovoltaic DC-to-AC converter, reactive power compensator, sends idle control command to photovoltaic DC-to-AC converter and reactive power compensator.

9) after waiting for that photovoltaic DC-to-AC converter, reactive power compensator execution instruction have been moved, return to step 1).

More than, by description of listed embodiment, the basic ideas and basic principles of the present invention are set forth.But the present invention is never limited to above-mentioned listed execution mode, every equivalent variations of doing based on technical scheme of the present invention, improvement and deliberately become of inferior quality behavior, all should belong to protection scope of the present invention.

Claims (5)

1. photovoltaic plant reactive power/voltage control method, is characterized in that, the method comprises the following steps:

1) measure the voltage instantaneous value U of photovoltaic electric station grid connection point _mea, calculating voltage instantaneous value U _meawith grid-connected point voltage desired value U _targetthe absolute value of difference, be designated as voltage deviation Δ U=|U _mea-U _target|;

2) the dead band threshold values δ of voltage deviation is set, enters step 3 if voltage deviation Δ U is greater than dead band threshold values δ), otherwise return to step 1);

3) by the system impedance X between self study method identification photovoltaic plant and electrical network;

4) calculate photovoltaic plant Target of Reactive Power value Q _target, $Q_{t\arg \mathrm{et}}=\frac{U_{t\arg \mathrm{et}}\×(U_{t\arg \mathrm{et}}-U_{\mathrm{mra}})}{X}+\frac{Q_{\mathrm{mea}}}{U_{\mathrm{mea}}}\×U_{t\arg \mathrm{et}},$ Wherein, Q _meafor the idle instantaneous value of photovoltaic electric station grid connection point;

5) judge whether each photovoltaic DC-to-AC converter and reactive power compensator meet predefined protection constraints, the photovoltaic DC-to-AC converter and the reactive power compensator that do not meet described protection constraints do not participate in reactive power/voltage control;

6) idle according to the preferential photovoltaic DC-to-AC converter that regulates, secondly regulate the idle principle of reactive power compensator, by Target of Reactive Power value Q _targetcarry out just sub-distribution, between photovoltaic DC-to-AC converter and reactive power compensator, distribute, the concrete steps of described just sub-distribution are:

A) calculate every the photovoltaic DC-to-AC converter that participates in reactive power/voltage control in photovoltaic plant, the idle adjustable upper limit value and lower limit value of reactive power compensator;

B) calculate photovoltaic plant Target of Reactive Power value Q _targetwith idle instantaneous value Q _meadifference, be designated as idle increment Delta Q=Q _target-Q _meaif idle increment Delta Q is greater than zero, go to step c), if idle increment Delta Q is less than zero, go to step d);

C), according to the idle adjustable higher limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle increasing nargin summation Q that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, reactive power compensator idle increasing nargin summation Q _cmargin, computing formula is as follows:

$\begin{array}{c}{Q}_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gi}\max }-Q_{\mathrm{Gimea}})\\ Q_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(Q_{\mathrm{Ci}\max }-Q_{\mathrm{Cimea}})\end{array}$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value, Q _gimaxfor the idle adjustable upper limit of every photovoltaic DC-to-AC converter, Q _cimaxfor the idle adjustable upper limit of every reactive power compensator;

D), according to the idle adjustable lower limit of photovoltaic DC-to-AC converter, reactive power compensator, calculate the idle nargin summation Q ' that subtracts that participates in the photovoltaic DC-to-AC converter of reactive power/voltage control in photovoltaic plant _gmargin, the idle nargin summation Q ' that subtracts of reactive power compensator _cmargin, computing formula is as follows:

$\begin{array}{c}{Q^{,}}_{\mathrm{Gm}\arg \mathrm{in}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(Q_{\mathrm{Gimea}}-Q_{\mathrm{Gi}\min })\\ {Q^{,}}_{\mathrm{Cm}\arg \mathrm{in}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(Q_{\mathrm{Cimea}}-Q_{\mathrm{Ci}\min })\end{array}$

Wherein, m, n are respectively photovoltaic DC-to-AC converter, reactive power compensator number of units, Q _gimea, Q _cimeabe respectively photovoltaic DC-to-AC converter, reactive power compensator is idle instantaneous value, Q _giminfor the idle adjustable lower limit of every photovoltaic DC-to-AC converter, Q _ciminfor the idle adjustable lower limit of every reactive power compensator;

7) according to the idle distribution principle of predefined unit, the result of first sub-distribution is carried out to sub-distribution again, respectively between photovoltaic DC-to-AC converter, distribute between reactive power compensator;

8) result of distributing according to photovoltaic DC-to-AC converter, reactive power compensator, sends idle control command to photovoltaic DC-to-AC converter and reactive power compensator;

9) after waiting for that photovoltaic DC-to-AC converter, reactive power compensator execution instruction have been moved, return to step 1).

2. photovoltaic plant reactive power/voltage control method according to claim 1, is characterized in that: in above-mentioned steps (3), described system impedance is arranged to upper lower limit value, in the time can not picking out system impedance, get its upper limit.

3. photovoltaic plant reactive power/voltage control method according to claim 1, is characterized in that: in above-mentioned steps (3), twice of the front and back voltage difference of system impedance is greater than 0.5% specified busbar voltage described in identification.

4. photovoltaic plant reactive power/voltage control method according to claim 1, is characterized in that: in above-mentioned steps (5), described protection constraints comprises the out-of-limit protective condition of analog quantity, quantity of state latch-up protection condition, communication disruption protective condition.

5. photovoltaic plant reactive power/voltage control method according to claim 1, is characterized in that: in above-mentioned steps (7), idle distribution principle comprises similar power factor, similar adjustment nargin, proportional with capacity.